'Seashell' hunting at Trentham Gardens

Mussels aren’t just for the seaside; they can be found in lakes and rivers too…

Can you spot any shells like these?

mussel shell biodiversity

Bigger than your average beach discovery, these are freshwater mussels, and they can be as big as 11cm long! The UK is home to six species of freshwater mussel. We have two types here at Trentham living in the river and the lake. They are:

Painters Mussel (Unio pictorum) - named because its shell was the perfect size for artists to use to mix paint colours.

Swollen River Mussel (Unio tumidus)

Conserving nature hidden from sight

Mussels sensitivity to water pollution, dam construction, dredging of river beds and declines in host fish (salmon and trout), threatens their survival globally. Their presence and size are great indicators of how healthy the estate's freshwater habitats are becoming.

These are not UK at-risk species (destroyed by people looking for freshwater pearls), but they are still animals protected by the Wildlife and Countryside Act.

Filter feeding bivalves

They are known as bivalves as they have two shells. They filter algae and bacteria from the water and help maintain clean water in aquatic habitats. It has been calculated that one adult mussel can filter as much as 40L of water per day.

Whilst growing in the riverbed they help stabilise sediment and provide shelter for small insects living in these habitats.

But why are they lying empty on the grass?

There are two predators who love to eat mussels here at Trentham. One is the resident otters who prise the shells open and eat the meaty mussel within. You can tell if it's an otter as the shell tends to be pretty intact and both halves are beside each other.

If you are eagle-eyed, you might even see the parting in the long grass where the otter has entered or exited the water nearby.

They also feed on the sand bars in the river as it passes the Garden Centre and Rivers of Grass, don't get too close to the edge, but have a look and see if any are there. 

Then there are the gulls. You will often see them dive into shallow water and fish out a mussel, then fly up into the air over some hard ground and drop the shell from a good height to break it open. You will see it causes quite a fuss when they do this as other gulls join in the race to grab the shell and take it off to somewhere quieter to eat, all the time being chased by other gulls! When gulls have opened the shells, they often have pecked holes in them or are quite broken.

If you find mussel shells, please leave them on the ground for others to enjoy discovering them but do share your photos with us using #trenthamgardens and #springwatch!

Special challenge for our photographers … we would love to see photos or videos of the gulls hunting in action!